System and method of stabilization of a gamma and neutron detecting device

ABSTRACT

A spectroscopic gamma and neutron detecting device includes a scintillation detector that detects gamma and thermal neutron radiation, the scintillation detector including signal detection and amplification electronics, and a stabilization module configured to measure a pulse height spectrum of neutron radiation, determine a thermal neutron peak position in the neutron pulse height spectrum originating from cosmic ray background radiation, monitor the thermal neutron peak position in the neutron pulse height spectrum during operation of the spectroscopic gamma and neutron detecting device, and adjust the signal detection and amplification electronics based on the thermal neutron peak position in the neutron pulse height spectrum, thereby stabilizing the spectroscopic gamma and neutron detecting device.

FIELD OF THE INVENTION

The present invention is generally directed to stabilization of a gammaand neutron detecting device.

BACKGROUND

Spectroscopic radiation measuring instruments require a high degree ofstability regarding the whole signal generation and processing chain.Some of these instruments contain a scintillation detector whichconverts ionizing radiation, such as X-rays, gamma rays, and electronsinto light, the number of photons being proportional to the energy ofthe ionizing radiation. These instruments typically also include aphoton detection assembly, such as a photomultiplier (PMT) or asemiconductor component (pin-diode or silicon photomultiplier) thatconverts the light of the scintillator into electric pulses and a dataprocessing system that comprises a multichannel analyzer (MCA), a dataprocessor and a data display unit. A higher number of photons produces ahigher pulse amplitude, the MCA producing a pulse height spectrum ofchannels arranged in order of increasing energy. See G. F. Knoll,Radiation Detection and Measurement, 3^(rd) Ed. (2000), (hereinafter“Knoll”) hereby incorporated by reference in its entirety (however,where anything in the incorporated reference contradicts anything statedin the present application, the present application prevails).

Temperature is a typical parameter that influences the whole signalprocessing chain, e.g., via the light output in the crystal oramplification in the photomultiplier. A common method to account forchanges in the temperature is the usage of a temperature sensor andsubsequent compensation of the amplification. The underlying temperaturedependency may either be generally assumed for a certain type ofinstrument or individually determined during factory calibration.

While this is an appropriate method to account for temperaturevariations, accounting for long-term drift and degradation effects ofe.g., the crystal quality and the optical coupling to the photondetection assembly and/or its amplification performance require adifferent approach. Conventional methods include stabilization to gammapeaks originating from background gamma radiation (e.g., K-40), or agamma check source such as Cs-137, Lu-176 or Na-22, which may bepermanently or temporarily attached to the detector. See U.S. Pat. No.7,544,927 B1 issued on Jun. 9, 2009, hereby incorporated by reference inits entirety (however, where anything in the incorporated referencecontradicts anything stated in the present application, the presentapplication prevails). These methods are prone to failure in elevatedgamma radiation fields or imply inconvenient regulatory issues due tothe usage and transport of radioactive material related to the checksource. Other approaches use time gated LED light pulses of definedpulse height or sophisticated digital signal processing techniquesanalyzing the time structure of the scintillation pulses.

There is, nevertheless, a need for further improvements in stabilizationof gamma and neutron detecting devices.

SUMMARY

In one embodiment, a method of stabilizing a spectroscopic gamma andneutron detecting device includes measuring a pulse height spectrum ofneutron radiation using a spectroscopic gamma and neutron detectingdevice that includes a scintillation detector that detects gamma andthermal neutron radiation, the scintillation detector including signaldetection and amplification electronics. The method then furtherincludes determining a thermal neutron peak position in the neutronpulse height spectrum originating from cosmic ray background radiation,monitoring the thermal neutron peak position in the neutron pulse heightspectrum during operation of the spectroscopic gamma and neutrondetecting device, and adjusting the signal detection and amplificationelectronics based on the thermal neutron peak position in the neutronpulse height spectrum, thereby stabilizing the spectroscopic gamma andneutron detecting device. The scintillation detector can include ascintillation crystal including at least 2 atomic % Li-6, such as aCerium (Ce)-doped Elpasolite having a chemical formula A₂LiLnX₆:Ce,wherein A is any one of Sodium (Na), Potassium (K), Rubidium (Rb), orCesium (Cs), Ln is any one of Scandium (Sc), Yttrium (Y), Lanthanum(La), or Lutetium (Lu), and X is any one of Bromine (Br) or iodine (I).In some embodiments, the scintillation crystal can be any one ofCs₂LiYCl₆:Ce (CLYC), Cs₂LiLaCl₆:Ce (CLLC), Cs₂LiLaBr₆:Ce (CLLB), orCs₂LiYBr₆:Ce (CLYB). In certain embodiments, determining the thermalneutron peak position in the neutron pulse height spectrum can includepulse shape discrimination (PSD) that distinguishes between gamma andneutron radiation.

In another embodiment, a spectroscopic gamma and neutron detectingdevice includes a scintillation detector that detects gamma and thermalneutron radiation, the scintillation detector including signal detectionand amplification electronics, and a stabilization module configured tomeasure a pulse height spectrum of neutron radiation, determine athermal neutron peak position in the neutron pulse height spectrumoriginating from cosmic ray background radiation, monitor the thermalneutron peak position in the neutron pulse height spectrum duringoperation of the spectroscopic gamma and neutron detecting device, andadjust the signal detection and amplification electronics based on thethermal neutron peak position in the neutron pulse height spectrum,thereby stabilizing the spectroscopic gamma and neutron detectingdevice. In some embodiments, the stabilization module can be furtherconfigured to include pulse shape discrimination (PSD) thatdistinguishes between gamma and neutron radiation to determine thethermal neutron peak position in the neutron pulse height spectrum. Thescintillation detector can include a scintillation crystal including atleast 2 atomic % Li-6, such as a Cerium (Ce)-doped Elpasolite having achemical formula A₂LiLnX₆:Ce, wherein A is any one of Sodium (Na),Potassium (K), Rubidium (Rb), or Cesium (Cs), Ln is any one of Scandium(Sc), Yttrium (Y), Lanthanum (La), or Lutetium (Lu), and X is any one ofBromine (Br) or iodine (I). In some embodiments, the scintillationcrystal can be any one of Cs₂LiYCl₆:Ce (CLYC), Cs₂LiLaCl₆:Ce (CLLC),Cs₂LiLaBr₆:Ce (CLLB), or Cs₂LiYBr₆:Ce (CLYB).

In yet another embodiment, a method of distinguishing between gamma andneutron counts recorded by a spectroscopic gamma and neutron detectingdevice includes providing a spectroscopic gamma and neutron detectingdevice that includes a scintillation detector that detects gamma andneutron radiation, the detecting device including pulse shapediscrimination (PSD) electronics that distinguish between gamma andneutron counts, and measuring a pulse height spectrum of gamma radiationcounts and a pulse height spectrum of neutron radiation counts using thedetecting device, both gamma and neutron radiation originating fromcosmic ray background radiation. The method then includes adjusting aPSD parameter based on a ratio between neutron radiation counts withenergy greater than a threshold neutron energy and a sum of gammaradiation counts with energy greater than a threshold gamma energy andneutron radiation counts with energy greater than the threshold neutronenergy. The threshold neutron energy can be 4 MeV, and the thresholdgamma energy can be 3 MeV. The scintillation detector is as describedabove.

In still another embodiment, a spectroscopic gamma and neutron detectingdevice includes a scintillation detector that detects gamma and neutronradiation, pulse shape discrimination (PSD) electronics that distinguishbetween gamma and neutron counts detected by the scintillation detector,and a PSD control module configured to measure a pulse height spectrumof gamma radiation counts and a pulse height spectrum of neutronradiation counts using the detecting device, both gamma and neutronradiation originating from cosmic ray background radiation, and adjust aPSD parameter based on a ratio between neutron radiation counts withenergy greater than a threshold neutron energy and a sum of gammaradiation counts with energy greater than a threshold gamma energy andneutron radiation counts with energy greater than the threshold neutronenergy. The threshold neutron energy, threshold gamma energy, andscintillation detector are as described above.

The invention has many advantages, including enabling stabilization ofspectroscopic gamma and neutron detecting devices without using anyconventional gamma check sources or any conventional neutron checksources such as AmBe or Cf-252.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a method of stabilizing a spectroscopic gammaand neutron detecting device according to an exemplary embodiment of theinvention.

FIG. 2 is a neutron pulse height spectrum of cosmic ray backgroundradiation showing neutron counts with energies in a range of between 0eV and 10 MeV.

FIG. 3 is a schematic illustration of a spectroscopic gamma and neutrondetecting device including a stabilization module according to anexemplary embodiment of the invention.

FIG. 4 is a flowchart of a method of distinguishing between gamma andneutron counts recorded by a spectroscopic gamma and neutron detectingdevice according to an exemplary embodiment of the invention.

FIG. 5 is a graph of measured cosmic false neutron relative contribution(%) with energies greater than 3 MeV as a function of PSD parameter.

FIG. 6 is a neutron pulse height spectrum with a PSD parameter of 142.

FIG. 7 is a neutron pulse height spectrum with a PSD parameter of 133.

FIG. 8 is a schematic illustration of a spectroscopic gamma and neutrondetecting device including a PSD control module according to anexemplary embodiment of the invention.

Like reference numerals refer to corresponding parts throughout theseveral views of the drawings.

DETAILED DESCRIPTION OF EMBODIMENTS

In the description of the invention herein, it is understood that a wordappearing in the singular encompasses its plural counterpart, and a wordappearing in the plural encompasses its singular counterpart, unlessimplicitly or explicitly understood or stated otherwise. Furthermore, itis understood that for any given component or embodiment describedherein, any of the possible candidates or alternatives listed for thatcomponent may generally be used individually or in combination with oneanother, unless implicitly or explicitly understood or stated otherwise.Moreover, it is to be appreciated that the figures, as shown herein, arenot necessarily drawn to scale, wherein some of the elements may bedrawn merely for clarity of the invention. Also, reference numerals maybe repeated among the various figures to show corresponding or analogouselements. Additionally, it will be understood that any list of suchcandidates or alternatives is merely illustrative, not limiting, unlessimplicitly or explicitly understood or stated otherwise. In addition,unless otherwise indicated, numbers expressing quantities ofingredients, constituents, reaction conditions and so forth used in thespecification and claims are to be understood as being modified by theterm “about.”

Accordingly, unless indicated to the contrary, the numerical parametersset forth in the specification and attached claims are approximationsthat may vary depending upon the desired properties sought to beobtained by the subject matter presented herein. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques. Notwithstandingthat the numerical ranges and parameters setting forth the broad scopeof the subject matter presented herein are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical values, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements.

Described herein are systems and methods of automatic spectralstabilization for scintillation detectors that are sensitive to bothgamma and thermal neutron radiation. Furthermore, performance tests andcalibration of the neutron detection capabilities of spectroscopic gammaand neutron detecting devices without requiring a conventional neutronsource such as AmBe or Cf-252 are described herein.

Spectroscopic scintillation detectors including at least 2 atomic %Li-6, such as a Cerium (Ce)-doped Elpasolite detect low energy neutronsby the Li-6 (n, α) H-3 reaction, which gives rise to a well-defined peakin the neutron related pulse height spectrum, that can be distinguishedfrom terrestrial gamma radiation by pulse height analysis, and furtherdistinguishable by pulse shape discrimination.

Since the neutron spectrum is virtually free of any other backgroundevents, the thermal neutron peak can be measured with high precisioneven for the low neutron fluence rate that relates to the neutronbackground radiation caused by the secondary cosmic radiation that ispresent on the surface of the earth. See U.S. patent application titled“Method of Operational Status Verification for a Neutron DetectingDevice,” attorney docket 20172US1/NAT, hereby incorporated by referencein its entirety (however, where anything in the incorporated referencecontradicts anything stated in the present application, the presentapplication prevails). The derived thermal neutron related peak positionin the spectrum can be used to stabilize the detector electronics inorder to compensate for any drift effect or degradation of the crystalperformance. In the absence of a man-made neutron source, the number ofcounts under the thermal neutron peak is a precise measure of thethermal neutron fluence of the natural background radiation. The systemsand methods described herein are also applicable at elevated gammaradiation levels as long as pile-up effects can be neglected, which istypically the case below 1,000 cps.

As shown in FIG. 1, a method 100 of stabilizing a spectroscopic gammaand neutron detecting device includes at step 110 measuring a pulseheight spectrum 200 of neutron radiation, as shown in FIG. 2, using aspectroscopic gamma and neutron detecting device 300 shown in FIG. 3that includes a scintillation detector 310 that detects gamma andthermal neutron radiation, the scintillation detector 310 includingsignal detection and amplification electronics. The method then furtherincludes at step 120 determining a thermal neutron peak position 210 inthe neutron pulse height spectrum 200 originating from cosmic raybackground radiation, monitoring at step 130 the thermal neutron peakposition 210 in the neutron pulse height spectrum 200 during operationof the spectroscopic gamma and neutron detecting device 300, and at step140 adjusting the signal detection and amplification electronics basedon the thermal neutron peak position 210 in the neutron pulse heightspectrum 200, thereby stabilizing the spectroscopic gamma and neutrondetecting device 300. Turning to FIG. 2, if the thermal neutron peakposition 210 drifts over time from channel 550 to channel 530, forexample, then the signal amplification by the signal detection andamplification electronics is adjusted to return the thermal neutron peakposition 210 back to channel 550, adjusting the sensitivity of thespectroscopic gamma and neutron detecting device 300 to both gamma andneutron radiation, thereby stabilizing the spectroscopic gamma andneutron detecting device 300. In one embodiment, the method 100 isimplemented in a computer program product carrying a computer programwhich, when loaded into a programmable processor, executes the method ofmonitoring the thermal neutron peak position in the neutron pulse heightspectrum and adjusting signal amplification based on the thermal neutronpeak position.

The scintillation detector 310 includes a scintillation crystalincluding at least 2 atomic % Li-6, such as a Cerium (Ce)-dopedElpasolite having a chemical formula A₂LiLnX₆:Ce, wherein A is any oneof Sodium (Na), Potassium (K), Rubidium (Rb), or Cesium (Cs), Ln is anyone of Scandium (Sc), Yttrium (Y), Lanthanum (La), or Lutetium (Lu), andX is any one of Bromine (Br) or iodine (I). In some embodiments, thescintillation crystal is any one of Cs₂LiYCl₆:Ce (CLYC), Cs₂LiLaCl₆:Ce(CLLC), Cs₂LiLaBr₆:Ce (CLLB), or Cs₂LiYBr₆:Ce (CLYB).

In certain embodiments, determining the thermal neutron peak position inthe neutron pulse height spectrum includes pulse shape discrimination(PSD) that distinguishes between gamma and neutron radiation, due to thedifferent rates of decay of the light generated by neutrons and gammaradiation. See Knoll.

In another embodiment, shown in FIG. 3, a spectroscopic gamma andneutron detecting device 300 includes a scintillation detector 310 thatdetects gamma and thermal neutron radiation, the scintillation detector310 including signal detection and amplification electronics, and astabilization module 320 configured to measure a pulse height spectrumof neutron radiation, determine a thermal neutron peak position in theneutron pulse height spectrum originating from cosmic ray backgroundradiation, monitor the thermal neutron peak position in the neutronpulse height spectrum during operation of the spectroscopic gamma andneutron detecting device, and adjust the signal detection andamplification electronics based on the thermal neutron peak position inthe neutron pulse height spectrum, thereby stabilizing the spectroscopicgamma and neutron detecting device. In some embodiments, thestabilization module can be further configured to include pulse shapediscrimination (PSD) as described above. The scintillation detector 310is as described above.

As described above, spectroscopic gamma and neutron detecting devicestypically include pulse shape discrimination (PSD) that distinguishesbetween gamma and neutron radiation. PSD electronics include a pulseshape (PSD) parameter that determines whether the event is recorded as aneutron or gamma radiation count. Described herein are systems andmethods of adjusting the PSD parameter using the neutron and theionizing part of the cosmic ray background radiation. If the total countrate is compatible with natural background radiation (typically lessthan 0.2 μSv/h), then the number of neutron counts with a pulse heightin the spectrum equivalent to an energy above a threshold neutron energyof typically 30% above the thermal neutron peak is very small. In theabsence of a high energy neutron source, which may give rise to neutronevents originating from fast neutron reactions in some crystals, such asCl-35 (n, p) S-35, the true ratio of registered fast neutrons reactionsto detected ionizing particles, such as muons, with energy greater thana threshold gamma energy (e.g., 3 MeV) is less than 0.001. As describedbelow, the PSD parameter is adjusted to match this known distribution ofnatural background radiation.

As shown in FIG. 4, a method 400 of distinguishing between gamma andneutron counts recorded by a spectroscopic gamma and neutron detectingdevice includes at step 410 providing a spectroscopic gamma and neutrondetecting device 300 as shown in FIG. 3 that includes a scintillationdetector 310 that detects gamma and neutron radiation as describedabove, the detecting device including pulse shape discrimination (PSD)electronics that distinguish between gamma and neutron counts, and atstep 420 measuring a pulse height spectrum of gamma radiation counts andat step 430 measure a pulse height spectrum of neutron radiation countsusing the detecting device, both gamma and neutron radiation originatingfrom cosmic ray background radiation.

The method then includes at step 440 adjusting a PSD parameter based ona ratio between neutron radiation counts with energy greater than athreshold neutron energy and a sum of gamma radiation counts with energygreater than a threshold gamma energy and neutron radiation counts withenergy greater than the threshold neutron energy. In some embodiments,the threshold neutron energy is 4 MeV, and the threshold gamma energy is3 MeV. See Kowatari et al., Sequential monitoring of cosmic-ray neutronsand ionizing components in Japan, presented at IRPA 11 Madrid, May 2004,and hereby incorporated by reference in its entirety (however, whereanything in the incorporated reference contradicts anything stated inthe present application, the present application prevails). A typicalvalue for the ratio is 0.05. A lower value, such as 0.01, would requiresampling 5 times longer for the same statistical accuracy. In oneembodiment, the method 400 is implemented in a computer program productcarrying a computer program which, when loaded into a programmableprocessor, executes the method of measuring a pulse height spectrum ofgamma radiation counts and a pulse height spectrum of neutron radiationcounts using the detecting device, and adjusting a PSD parameter basedon a ratio between neutron radiation counts with energy greater than athreshold neutron energy and a sum of gamma radiation counts with energygreater than a threshold gamma energy and neutron radiation counts withenergy greater than the threshold neutron energy.

An example of the influence of the PSD parameter on the counts recordedas neutrons with energy greater than 3 MeV, that is, actual muonsrecorded incorrectly as neutrons, is shown in FIG. 5 for cosmic raybackground radiation at an altitude of 330 m recorded for 10,000seconds. As the PSD parameter increases, the recorded relative percentcontribution of events with energy greater than 3 MeV recordedincorrectly as neutrons increases. As shown in FIG. 6, for a PSDparameter of 142, the neutron pulse height spectrum shows many countsrecorded in the channels for energy greater than 3 MeV indicated byarrow 610. By contrast, processing the same data with a PSD parameter of133 yields the neutron pulse height spectrum shown in FIG. 7, with fewcounts recorded in the channels for energy greater than 3 MeV indicatedby arrow 710, with those events recorded correctly as muons in the gammapulse height spectrum (not shown).

In still another embodiment shown in FIG. 8, a spectroscopic gamma andneutron detecting device 800 includes a scintillation detector 810 thatdetects gamma and neutron radiation, pulse shape discrimination (PSD)electronics that distinguish between gamma and neutron counts detectedby the scintillation detector, and a PSD control module 820 configuredto measure a pulse height spectrum of gamma radiation counts and a pulseheight spectrum of neutron radiation counts using the detecting device,both gamma and neutron radiation originating from cosmic ray backgroundradiation, and adjust a PSD parameter based on a ratio between neutronradiation counts with energy greater than a threshold neutron energy anda sum of gamma radiation counts with energy greater than a thresholdgamma energy and neutron radiation counts with energy greater than thethreshold neutron energy. The threshold neutron energy, threshold gammaenergy, and scintillation detector are as described above.

While the present invention has been illustrated by a description ofexemplary embodiments and while these embodiments have been described inconsiderable detail, it is not the intention of the applicant torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. The invention in its broader aspects istherefore not limited to the specific details, representative apparatusand method, and illustrative example shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of applicant's general inventive concept.

What is claimed is:
 1. A method of stabilizing a spectroscopic gamma andneutron detecting device, the method comprising: a. measuring a pulseheight spectrum of neutron radiation using a spectroscopic gamma andneutron detecting device that includes a scintillation detector thatdetects gamma and thermal neutron radiation, the scintillation detectorincluding signal detection and amplification electronics; b. determininga thermal neutron peak position in the neutron pulse height spectrumoriginating from cosmic ray background radiation; c. monitoring thethermal neutron peak position in the neutron pulse height spectrumduring operation of the spectroscopic gamma and neutron detectingdevice; and d. adjusting the signal detection and amplificationelectronics based on the thermal neutron peak position in the neutronpulse height spectrum, thereby stabilizing the spectroscopic gamma andneutron detecting device.
 2. The method of claim 1, wherein thescintillation detector comprises a scintillation crystal including atleast 2 atomic % Li-6.
 3. The method of claim 2, wherein thescintillation crystal is a Cerium (Ce)-doped Elpasolite having achemical formula A₂LiLnX₆:Ce, wherein A is any one of Sodium (Na),Potassium (K), Rubidium (Rb), or Cesium (Cs), Ln is any one of Scandium(Sc), Yttrium (Y), Lanthanum (La), or Lutetium (Lu), and X is any one ofBromine (Br) or iodine (I).
 4. The method of claim 3, wherein thescintillation crystal is any one of Cs₂LiYCl₆:Ce (CLYC), Cs₂LiLaCl₆:Ce(CLLC), Cs₂LiLaBr₆:Ce (CLLB), or Cs₂LiYBr₆:Ce (CLYB).
 5. The method ofclaim 1, wherein determining the thermal neutron peak position in theneutron pulse height spectrum includes pulse shape discrimination (PSD)that distinguishes between gamma and neutron radiation.
 6. Aspectroscopic gamma and neutron detecting device comprising: a. ascintillation detector that detects gamma and thermal neutron radiation,the scintillation detector including signal detection and amplificationelectronics; and b. a stabilization module configured to: i. measure apulse height spectrum of neutron radiation; ii. determine a thermalneutron peak position in the neutron pulse height spectrum originatingfrom cosmic ray background radiation; iii. monitor the thermal neutronpeak position in the neutron pulse height spectrum during operation ofthe spectroscopic gamma and neutron detecting device; and iv. adjust thesignal detection and amplification electronics based on the thermalneutron peak position in the neutron pulse height spectrum, therebystabilizing the spectroscopic gamma and neutron detecting device.
 7. Thedevice of claim 6, wherein the scintillation detector comprises ascintillation crystal including at least 2 atomic % Li-6.
 8. The deviceof claim 7, wherein the scintillation crystal is a Cerium (Ce)-dopedElpasolite having a chemical formula A₂LiLnX₆:Ce, wherein A is any oneof Sodium (Na), Potassium (K), Rubidium (Rb), or Cesium (Cs), Ln is anyone of Scandium (Sc), Yttrium (Y), Lanthanum (La), or Lutetium (Lu), andX is any one of Bromine (Br) or iodine (I).
 9. The device of claim 8,wherein the scintillation crystal is one of Cs₂LiYCl₆:Ce (CLYC),Cs₂LiLaCl₆:Ce (CLLC), Cs₂LiLaBr₆:Ce (CLLB), or Cs₂LiYBr₆:Ce (CLYB). 10.The device of claim 6, wherein the stabilization module is furtherconfigured to include pulse shape discrimination (PSD) thatdistinguishes between gamma and neutron radiation to determine thethermal neutron peak position in the neutron pulse height spectrum. 11.A computer program product carrying a computer program which, whenloaded into a programmable processor, executes the method of: a.measuring a pulse height spectrum of neutron radiation using aspectroscopic gamma and neutron detecting device that includes ascintillation detector that detects gamma and thermal neutron radiation,the scintillation detector including signal detection and amplificationelectronics; b. determining a thermal neutron peak position in theneutron pulse height spectrum originating from cosmic ray backgroundradiation; c. monitoring the thermal neutron peak position in theneutron pulse height spectrum during operation of the spectroscopicgamma and neutron detecting device; and d. adjusting the signaldetection and amplification electronics based on the thermal neutronpeak position in the neutron pulse height spectrum, thereby stabilizingthe spectroscopic gamma and neutron detecting device.
 12. The computerprogram product of claim 11, wherein the scintillation detectorcomprises a scintillation crystal including at least 2 atomic % Li-6.13. The computer program product of claim 12, wherein the scintillationcrystal is a Cerium (Ce)-doped Elpasolite having a chemical formulaA₂LiLnX₆:Ce, wherein A is any one of Sodium (Na), Potassium (K),Rubidium (Rb), or Cesium (Cs), Ln is any one of Scandium (Sc), Yttrium(Y), Lanthanum (La), or Lutetium (Lu), and X is any one of Bromine (Br)or iodine (I).
 14. The computer program product of claim 13, wherein thescintillation crystal is any one of Cs₂LiYCl₆:Ce (CLYC), Cs₂LiLaCl₆:Ce(CLLC), Cs₂LiLaBr₆:Ce (CLLB), or Cs₂LiYBr₆:Ce (CLYB).
 15. The computerprogram product of claim 11, wherein determining the thermal neutronpeak position in the neutron pulse height spectrum includes pulse shapediscrimination (PSD) that distinguishes between gamma and neutronradiation.
 16. A method of distinguishing between gamma and neutroncounts recorded by a spectroscopic gamma and neutron detecting device,the method comprising: a. providing a spectroscopic gamma and neutrondetecting device that includes a scintillation detector that detectsgamma and neutron radiation, the detecting device including pulse shapediscrimination (PSD) electronics that distinguish between gamma andneutron counts; b. measuring a pulse height spectrum of gamma radiationcounts originating from cosmic ray background radiation using thedetecting device; c. measuring a pulse height spectrum of neutronradiation counts originating from cosmic ray background using thedetecting device; and d. adjusting a PSD parameter based on a ratiobetween neutron radiation counts with energy greater than a thresholdneutron energy and a sum of gamma radiation counts with energy greaterthan a threshold gamma energy and neutron radiation counts with energygreater than the threshold neutron energy.
 17. The method of claim 16,wherein the threshold neutron energy is 4 MeV and the threshold gammaenergy is 3 MeV.
 18. The method of claim 16, wherein the scintillationdetector comprises a scintillation crystal including at least 2 atomic %Li-6.
 19. The method of claim 18, wherein the scintillation crystal is aCerium (Ce)-doped Elpasolite having a chemical formula A₂LiLnX₆:Ce,wherein A is any one of Sodium (Na), Potassium (K), Rubidium (Rb), orCesium (Cs), Ln is any one of Scandium (Sc), Yttrium (Y), Lanthanum(La), or Lutetium (Lu), and X is any one of Bromine (Br) or iodine (I).20. The method of claim 19, wherein the scintillation crystal is one ofCs₂LiYCl₆:Ce (CLYC), Cs₂LiLaCl₆:Ce (CLLC), Cs₂LiLaBr₆:Ce (CLLB), orCs₂LiYBr₆:Ce (CLYB).
 21. A spectroscopic gamma and neutron detectingdevice comprising: a. a scintillation detector that detects gamma andneutron radiation; b. pulse shape discrimination (PSD) electronics thatdistinguish between gamma and neutron counts detected by thescintillation detector; and c. a PSD control module configured to: i.measure a pulse height spectrum of gamma radiation counts originatingfrom cosmic ray background radiation using the detecting device; ii.measure a pulse height spectrum of neutron radiation counts originatingfrom cosmic ray background radiation using the detecting device; andiii. adjust a PSD parameter based on a ratio between neutron radiationcounts with energy greater than a threshold neutron energy and a sum ofgamma radiation counts with energy greater than a threshold gamma energyand neutron radiation counts with energy greater than the thresholdneutron energy.
 22. The device of claim 21, wherein the thresholdneutron energy is 4 MeV and the threshold gamma energy is 3 MeV.
 23. Thedevice of claim 21, wherein the scintillation detector comprises ascintillation crystal including at least 2 atomic % Li-6.
 24. The deviceof claim 23, wherein the scintillation crystal is a Cerium (Ce)-dopedElpasolite having a chemical formula A₂LiLnX₆:Ce, wherein A is any oneof Sodium (Na), Potassium (K), Rubidium (Rb), or Cesium (Cs), Ln is anyone of Scandium (Sc), Yttrium (Y), Lanthanum (La), or Lutetium (Lu), andX is any one of Bromine (Br) or iodine (I).
 25. The device of claim 24,wherein the scintillation crystal is one of Cs₂LiYCl₆:Ce (CLYC),Cs₂LiLaCl₆:Ce (CLLC), Cs₂LiLaBr₆:Ce (CLLB), or Cs₂LiYBr₆:Ce (CLYB). 26.A computer program product carrying a computer program which, whenloaded into a programmable processor, executes the method of: a.measuring a pulse height spectrum of gamma radiation counts originatingfrom cosmic ray background radiation using a spectroscopic gamma andneutron detecting device that includes a scintillation detector thatdetects gamma and neutron radiation, the detecting device includingpulse shape discrimination (PSD) electronics that distinguish betweengamma and neutron counts; b. measuring a pulse height spectrum ofneutron radiation counts originating from cosmic ray background usingthe detecting device; and c. adjusting a PSD parameter based on a ratiobetween neutron radiation counts with energy greater than a thresholdneutron energy and a sum of gamma radiation counts with energy greaterthan a threshold gamma energy and neutron radiation counts with energygreater than the threshold neutron energy.
 27. The computer programproduct of claim 26, wherein the threshold neutron energy is 4 MeV andthe threshold gamma energy is 3 MeV.
 28. The computer program product ofclaim 26, wherein the scintillation detector comprises a scintillationcrystal including at least 2 atomic % Li-6.
 29. The computer programproduct of claim 28, wherein the scintillation crystal is a Cerium(Ce)-doped Elpasolite having a chemical formula A₂LiLnX₆:Ce, wherein Ais any one of Sodium (Na), Potassium (K), Rubidium (Rb), or Cesium (Cs),Ln is any one of Scandium (Sc), Yttrium (Y), Lanthanum (La), or Lutetium(Lu), and X is any one of Bromine (Br) or iodine (I).
 30. The computerprogram product of claim 29, wherein the scintillation crystal is one ofCs₂LiYCl₆:Ce (CLYC), Cs₂LiLaCl₆:Ce (CLLC), Cs₂LiLaBr₆:Ce (CLLB), orCs₂LiYBr₆:Ce (CLYB).